I've been to the L13 facility. The owner is a very nice guy, and showed me the operation. He was coating some of the bullets while I was there.
Yes, the coating is powder coat. He tumbles the bullets with the powder, runs them through an oven, and repeats to ensure complete coverage.
The bullets are from the same molds he uses for his cast lead bullets, so they have the lube grooves. My preference would be to have coated bullets without a lube groove, as the groove is not needed. This would leave more bearing surface which, I think, would make them more accurate.
I've only shot a few test samples that he gave me, in 9mm and 40. They seemed accurate enough and I got decent velocity spreads with them.
In the 40, I noticed what appeared to be a little leading, but just on the lands of the rifling, not the grooves. I did not notice this on the 9mm, but with the 9mm, I shot the L13 first and then followed up with some plated loads I had worked up, so I don't know if the plated bullets helped clear away any leading or not.
I know several guys in this area that use them and really like them.